Daylight developing tank



Sept. 6, 1955 M. LESJAK 2,716,931

DAYLIGHT DEVELOPING TANK Filed Aug. 23, 1952 INVENTOR MICHAEL LESJAKDEQHSIED 8, BABE? TE LESJ/MI ADMINISTRAT/FIX BY g e m m ATTORNEYS United States Patent DAYLIGHT DEVELOPING TANK Michael Lesjak, deceased, late of Iclreuhausen, near Augsburg, Germany, by Babette Viktoria Lesjak, administratn'x, Goggingen, Germany Application August 23, 1952, Serial No. 305,946 Claims priority, application Germany September 20, 1951 8 Claims. (Cl. 9590.5)

This invention relates to an improvement in devices for the developing, fixing and washing of light-sensitive strips, whereby the exposed strip may be wound up in a light-tight closeable fluid container upon a manually operable core which is rotatably mounted within the closed container. More particularly, this invention relates to an improvement in a daylight developing tank for developing photographic film strips with perforated edges such as is disclosed in my copending application for U. S. Letters Patent, Serial No. 257,167, filed on November 19, 1951. Specifically the invention relates to an improvement in such type daylight developing tank whereby a convolutely wound photographic film strip having spaced perforations along its sides, may be unreeled from a storage member or casing onto an actuating core along a spiral path while being freely suspended in a liquid developing bath without the benefit of conventional fixed helical guide means.

in daylight developing tanks of the type disclosed in said application, the prior art helical film guide structures and pull-in bands have been eliminated by utilizing the inherent resiliency of the rolled film strip to keep the surfaces of the film convolutions separated while the freedom of movement of the film is simultaneously availed of to agitate the developing fluid bath by causing it to transcribe wandering loop-like undulations. As is more fully described in said prior application, such innovation is attained by unwinding the leading end of an exposed photographic film strip from a conventional cassette or roll film spool, mounted in the film storage chamber of the tank, and connecting it to a rotatable core member, mounted in the developing chamber of the tank, in such manner that initial rotation of the core member will wind the film thereon in a direction opposite to that from which it is uncurled from the cassette or roll film spool. After all of the exposed portion of the film strip has been uncurled from the cassette or roll film spool, the trailing end thereof is clamped against the tank casing to firmly anchor it and the core member is then rotated to repeatedly spool and unspool the film strip thereon, the inherent resiliency and tend ency of the strip to return to its initial curled condition causing it to transcribe a wandering loop effect to agitate the developing fluid and ensure a complete and equal development of all portions of the film.

It often happens, however, that the entire film strip is pulled free of its storage cassette or roll film spool before the trailing end thereof can be clamped against the tank casing. When this happens the formation of the wandering loop eifect is precluded and the proper development of the film is not possible.

In order to avoid this difficulty it has previously been proposed to provide a measuring roller and a clamping device adjacent the cassette in the container in order to enable the operator to clamp the trailing end of the unwound film after reeling off a specified length from the storage cassette to the rotatable core. This device, however, has not completely eliminated the above-noted "ice drawbacks because the lengths of strips which are desired to be treated vary widely and accurate determination of the extent of the film is often difficult Without laborious pre-developing measuring procedures.

Accordingly, it is the prime purpose of the instant invention to provide a securing means for automatically retaining the trailing edge of an exposed wound film strip whenever it may be inadvertently separated from its storage member regardless of the form of such member, i. e. a cassette or a spool or reel. It is an object of the instant invention that an automatic strip retaining and restraining mechanism be provided which will function to automatically secure the free trailing edge of an unwound film strip regardless of the length of the strip. It is a further object of the invention to provide such retaining and restraining device which will not destroy the unwound flexing and undulating character of the freely convolutely wound strip during either its winding or unwinding upon or from the rotatable core member of the tank.

The invention may be broadly described as consisting of a single stop unit having spaced hooks and which is positioned in the developing chamber adjacent to but not in the normal path of movement of the film strip as it is uncurled from the storage cassette or spool onto the core member. The stop unit is preferably fabricated from sheet material to have a geometric configuration of substantially ogee curvature with the hooks positioned at one trailing end of the curved sheet. In accordance with a preferred embodiment of the present invention these film securing hooks may be expediently fashioned to project from a V-shaped metal sheet having a U- shaped free end, reversed in direction from said V portion, and adapted to be readily and interchangeably mounted upon the separating partition within said tank. Preferably, the V -shaped portion of the sheet is positioned to extend into the developing chamber and includes integral, laterally extending flanges which abut the side walls of the chamber to accurately position the sheet and its securing hooks in a predetermined location therein. In practice, it has been found desirable to locate the hooks between two to three perforation lengths aside, and approximately two perforation lengths below, the upper edge of the partition separating the film storage chamber from the developing chamber. It will be obvious from the description and illustrations which accompany this disclosure that it will be possible to mount the instant retaining and restraining mechanism upon a daylight developing tank of difierent construction for the same purpose.

Having generally described the invention, it will now be more particularly defined by way of reference to the accompanying drawings in which:

Fig. l is a side view in section of the developing tank with the cover placed thereon at the beginning of the spooling-in step.

Fig. 2.is a similar view after the free end of the film has left the cassette but before it has fallen into the holding hooks.

Fig. 3 shows the device after the film end has fallen into the holding hooks, and

Fig. 4 is a perspective view of the catching sheet with its holding hooks.

The daylight developing tan consists of two chambers, a storage reel or cassette chamber 1 within which a roll film reel or cassette 2 is placed, and a developing chamber 3. A rotatable core 4 is rotatably mounted in cham ber 3 and upon which the film strip 5 is unreeled after attaching the leading edge of the film to the core with the aid of an attaching or clamping device 6. Uncurling of the film from storage cassette 2 to core 4 takes place as may be seen from the arrow A in Fig. l, at the beginning in a counterclockwise direction. A cover, which closes the top of the daylight developing tank in a light-tight manner, is indicated by 7. The developing tank further includes a rotatable bow 8 positioned on the cover 7 and arranged so that it may clamp the end of the film strip against the partition 9 or some other suitable part, for example, the V-shaped stop sheet 10, upon pivoting in a downward direction.

According to the invention a film strip restraining and retaining stop sheet 10 is mounted over the partition 9 which separates the developing chamber 3 from the cassette chamber 1. This sheet includes a pair of holding hooks 10a, lateral projections 10b and a U-shaped bentover, free end me. This U-shaped bent-over end may be placed over and depend from the partition 9 and rests with its flange projections 1012 upon the side ledges 11 of the developing chamber 3 to accurately position the sheet within the container. The film stopping or catching sheet 10 is so shaped and the hooks 10a are so arranged that the latter come to rest closely beside and shortly below the upper edge of the partition 9. The distance of the hooks 100 from the partition 9 should, in the case of movie film, be between 6 to 12 mm. if the film strip is now drawn out of and separated from the storage reel or cassette 2 by the turning of the core 4, the free bent end a of the film, due to its being curved upon insertion in mem her 2 and its inherent tendency to curl up, will automatically become caught with its side perforations overlying the hooks a.

There it may be held securely, as may be seen from Fig. 3 by means of the pivoted bow 3. The film strip 5 can then be unwound from and again wound onto the core 4 without there being any danger that the free trailing end 50 of the film 5 will slip through or be torn out of the restraining device 10. It should be noted that regardless of the speed of the winding action of core 4, experience has shown that the retaining hooks 10a, in the position shown, always enter into the next to the last perforation hole of the film strip, thus insuring a complete development of all exposed portions of the strip. As will be apparent from an inspection of Figs. 1 through 3 inclusive, the stop unit 10 is so positioned that the film catching and retaining hooks 1001 are below the path of and do not interfere with the free movement of the film 5 as it is uncurled from the cassette 2 onto the core member 4 unless the free trailing end of the film strip has become separated from the cassette. At such time the film strip flexes out of its normal path of movement and onto the stop limit 10 where its curled end will be caught on hooks 10a.

One of the particular advantages of the instant film clamping device resides in the fact that the inherent resiliency of the wound strip is utilized to insure the automatic securing of the trailing end of the strip upon the stop device 10. It will be apparent that as the bent, trailing end of the strip is drawn over the partition 9, it will be snapped directly downward onto the protruding prongs 10a and be caught and retained there, without any need for manual supervision and independent of the length of the film strip.

As many apparently widely different embodiments of this invention may be made without departing from the spirit and scope hereof, it is to be understood that the above invention is not limited except as defined in the appended claims.

What is claimed is:

1. in a daylight developing tank for developing lightsensitive film strips and including an enclosed, covered tank divided into a pair of chambers separated by a partition wall and having a rotatable film strip receiving core member in one chamber and a storage member for said film strips in the other chamber, the improvement which comprises an automatic stationary, film strip catching device positioned intermediate said two members and including structure for catching and retaining the trailing end of a film strip as it is unwound from the storage member to the core member, said device being located adjacent to but below the normal path of movement of said film strip between said members.

2. The combination set forth in claim 1 in which said device is formed as a bent sheet having a pair of integral, spaced, upwardly extending, film-strip engaging prongs thereon.

3. The combination set forth in claim 1 in which said device is formed as a bent sheet having an ogee curvature and includes a pair of spaced film-strip catching prongs adjacent one end of said sheet.

4. The combination set forth in claim 3 in which the ogee curvature of said sheet depicts a V-shaped configurgation having one leg of the V terminating in an inverted U-shaped tail portion.

5. The combination set forth in claim 4 in which said inverted U-shaped tail is positioned to overlie and grip the edge of said partition wall.

6. The combination set forth in claim 5 in which a second film-strip controlling device is pivoted in said tank adjacent said partition wall and is adapted to abut said device and retain said film strip therebetween.

7. A film-strip catching and retaining device for automatically arresting free movement of the trailing edge of a wound film-strip in a daylight developing tank comprising a bent sheet having a predominant geometric configuration of an ogee curvature and including a pair of spaced film-strip catching projections along one edge thereof.

8. The combination set forth in claim 1 in which said device includes structure for anchoring it to said partition wall.

References Cited in the file of this patent UNITED STATES PATENTS 899,495 Abbott Sept. 29, 1908 2,232,763 Becher Feb. 25, 1941 2,498,477 Alk Feb. 21, 1950 FOREIGN PATENTS 902,968 France Jan. 5, 1945 

